More than 200 migrant workers staged a violent protest outside a township government building in Chaozhou, Guangdong, authorities have confirmed.

Witnesses said the protest on Monday degenerated into a riot that eventually involved thousands of migrant workers and local residents.

Chaoan county police released a brief statement yesterday morning saying police dispersed the crowd in front of the Guxiang township government building by about 10.30pm on Monday.

Police said protesters smashed at least three cars and another one was burned, and nine people suspected of involvement in the unrest had been arrested.

The statement did not say how many people were injured.

In a video posted online, angry people can be seen rushing into the street, throwing rocks at cars, mobbing government buildings and smashing police vehicles. Migrant workers also fought local residents.

Witnesses said many shops in Guxiang remain closed and many migrant workers have left the township because they feared revenge attacks from locals.

Police said the protest was led by a migrant worker from Sichuan province who is employed by a ceramics workshop. He was wounded in a knife attack after demanding unpaid wages from his boss last Wednesday, they said. Three people have been arrested for the knife attack.

However, the Sichuan migrant's relatives said he and his 19-year-old son went to the ceramics workshop to demand 3,000 yuan (HK$3,600) in back pay. The father was beaten and his son's hands and feet were badly chopped by the boss and two other men, all Chaoan natives.

The next day, dozens of workers from Sichuan gathered at the government building and called for the three men who attacked the father and son to be arrested. Anger soon spread among Chaoan's migrant workers after several protesters were detained while those responsible for the attack remained free.

'We had never called on those migrant workers for help,' a relative of the man and his son said. 'They came to protest because we've all been owed back-pay by local bosses for a long time and the local authorities have given us little help.'

The boss and the other two men involved in the assault were detained by Sunday but the unrest worsened anyway.